Technology of Cell Based Meat and the Components Involved
Cell-based meat production is an evolving revolution in cellular agriculture. It involves production of meat by cultivating cells in laboratories rather than animal slaughter. The cell-culture technology is adopted in the production process. This technology synergises tissue engineering techniques, biotechnology and some other biological and synthetic processes.
Cell-based meat is made by extracting cells from animals and then feeding the cells to the point where they grow into muscle tissue, which is the main constituent of meat. There are four major requirements for culturing cell-based meat, which are, cell lines or stem cells, growth medium, scaffold and bioreactors.
Starter cell selection
Generally, cellular agriculture requires starter cells. In cell-based meat production, primary cell samples which are extracted directly from the animals or stem cells can be used. Stem cells are the root cells from which other cells with exclusive functions grow. They have the capacity to multiply and produce many other specialized cells, including muscles and organs. The cell samples can be extracted from animals, fresh meat or cell banks.
The selection of starter cells is aimed at making the right choice of cells that end up with a speedy growth rate, a similar texture to the conventional animal meat and a great taste. Primary cells are usually fully formed, and so they produce other cells, which are their replica. The downside to them is that they do not multiply rapidly.
On the other hand, the possibilities that abound with stem cells are endless as they can be multiplied into many different kinds of cells depending on the constituents of their environment. Stem cells have a rapid multiplication rate, easily metamorphose into tissues, and have more enduring life spans than primary cells. These characteristics usually differ from cell to cell depending on the originating source; hence the cultivation process adopted must be adjusted to suit the kind of cells being used. A single cell has the ability to yield many daughter cells, which end up producing large quantities of cell-based meat, and this production rate is capable of meeting today’s world demand for meat.
Growth medium treatment
The next step in the production process after the selection of the cells is to soak them in a growth medium so that they can multiply rapidly. Growth media are usually made from base media which contain nutrients like proteins, fats, carbohydrates and vitamins that are essential for the multiplication of cells. They must therefore be in a form that makes them accessible to the cells since they do not possess a digestive system.
Serum is an important component of the growth media. It is used to incorporate the growth factors into the medium and also contains inhibitors. Serums help to control the pH of the media, aid the attachment of cells to substrates, and reduce the risk of damages caused by viscosity. Some other important components of growth media are antibiotics, which help to prevent the manifestation of fungal and bacterial impurities and trace elements, which are essential for biological processes.
The media to be used is determined by the type of cells being used for the process. Media may be natural or artificial. Natural media are made from naturally occurring biological substances, but their constituents are not easily identifiable, so they are not reproducible. Artificial media are prepared by the combination of different organic and inorganic nutrients and substances. They can be serum-containing, protein-free, serum-free or chemically defined. In addition, growth media are available in powder or liquid form. The powder form is the most cost-effective but requires sterilization before use.
Scaffolding
After the cells have been introduced into a growth medium, the next step is scaffolding. The goal of scaffolding in meat culture is to create a mould that forms the basis for the shape and structure of the resultant meat product. It is of utmost importance to ensure that the cells used in the production of lab-grown meat are able to access some form of mechanical support. When cells are in the body of the animal, collagen structures and other internal structures (which are altogether known as the extracellular matrix—ECM) give them form. The goal of scaffolding in cell culture is to replicate similar structures outside the animal body, which possess a solid three-dimensional structure and are also edible. Researchers have made several attempts at achieving this. An example is the seeding of cultured cells unto the structures of plants like spinach, which satisfies the prerequisites of the ability to provide a three-dimensional support framework for the cultured cells and edibility.
Scaffold materials also need to possess certain other important characteristics asides from the three-dimensional structure and edibility to aid their functionality. They must be porous so that they can evacuate any cellular constituents that may hinder the proper formation of tissues. They also need to be degradable so that they are separable from the finished product at the end of the culture process. The disposal of the degradable materials afterwards also needs to be carefully considered. In addition, they should possess biochemical properties similar to those of the extracellular matrix to promote cell adhesion. Chitin, collagen, nanomaterials and cellulose are important components of scaffolds.
Bioreactors
The next step in the production process is the placement of the scaffolds in a bioreactor to enable the growth and specialization of cells. A bioreactor is a huge piece of equipment that has the capacity to aid the replication and multiplication of cells by exposing them to various kinds of environmental factors. The temperature in the bioreactor must be similar to what is obtainable when the cells grow within the animal body. Usually, a temperature of 37°C is required for mammals, while room temperature is just sufficient for insect cells. The level of carbon dioxide required for most bioreactors is 5%.
Generally, the method of cultivation may be continuous, batch, fed-batch or perfusion. In the continuous process, cells are cultivated in a vessel and supplied with fresh media. The products are then collected in another vessel. The batch process involves cultivating cells in a specified quantity of media to ensure growth to the highest possible density. In the fed-batch method, the infusion, culture and collection of cells are executed in one stream. Perfusion branches off from the continuous method; the difference is that it allows for the possibility of employing recycled media in the process.
There are different types of bioreactor designs. The most commonly adopted bioreactor is the stirred tank type. It contains an impeller which speeds up the flow and ensures that the culture media coalesces. It also contains a diffuser that transports oxygen into the media. The stirred-tank bioreactors are commonly used for suspended cultures. For adherent culture, feed bioreactors are more commonly adopted. They have fibre strips that are put together to produce a bed for cells to cling to. The culture medium that has been aerated is distributed throughout the bed. The culture media is converted into a gaseous form in airlift bioreactors utilizing air bubbles. These bubbles are subsequently disseminated and dispersed among the cells. Continuous culture is commonly done in perfusion bioreactors. They continuously drain lactic acid-saturated, nutrient-depleted media and replace it with replenished media.